This invention relates to systems and methods for remote actuation or control of tools and completion equipment in gas and oil wells, whether in subsurface or subsea locations, for communication and control in measurement while drilling (MWD) systems and associated tools, and for remote control of traveling bodies and stationary elements in pipeline installations.
As oil and gas drilling and production techniques have advanced and become more complex and versatile, many different down-hole tools have come into use. Some include their own power packs, or other energy sources, and either are or can potentially be operated by remote control. Microprocessors, which are small, reliable and have a low power consumption, are commonly used in such tools and equipment. There are many other potential applications for remote control of tools and other equipment within a confining passageway at a substantial distance, including not only in the drilling, completion, workover, production and abandonment of a well, but also in tools and devices that are fixed or movable in pipelines and further with underwater equipment connected to a surface system via a subsea manifold. If commands can reliably be communicated to a remote well bore location, then such functions as opening and closing valves, sliding sleeves, inflating plugs, detonating perforating guns, shifting tools and setting packers are available. Through the use of remote actuation, expensive down time in the well can be minimized, saving the costs of many hours or even days of operation.
Systems have been proposed, and some are in use, for remote control of equipment in well bore installations. A wire connection system using electric line has been in use for some time, and remains in use today. This system employs a heavy duty electrical line that is fed into the well bore along the tubing or casing string to the down-hole location. The line is of relatively large diameter and for setup requires a massive carrier and support equipment, with setup time requiring many hours. Moreover, electrical power transmitted into a deep well creates potential dangers from short circuits and arcing in explosive environments at the well site where an inert atmosphere cannot be maintained. A later developed xe2x80x9cSlicklinexe2x80x9d is only a wire for providing mechanical operations and is of much smaller diameter although very high strength. While it can be transported and manipulated by much smaller vehicles and installations, and is deployed considerably more rapidly than the electric line mechanism, it is not well suited to remote operation of down-hole tools. Time consuming and unsafe control methods with these systems are based on use of times, and motion sequences combined with , pressure and temperature readings.
Other systems are known for transmitting non-electrical commands to preinstalled down-hole tools by communicating through a pressurized liquid medium or metal walls along the well bore. Pressure variations imparted at the surface are sensed by a strain gauge or other transducer at the remote location, to trigger a battery powered device in response to a coded pressure varying signal. One such system, called the xe2x80x9cEDGExe2x80x9d (trademark of Baker Hughes) system, interfaces with liquid media only and injects pulses of chosen frequency into the well bore. A down-hole tool having an actuable element powered at the tool includes electronic circuits which filter the selected frequency from other variations and respond to a selected pattern of pulse frequencies. This system requires substantial setup time and can only be used in a constant and predictable all-liquid bore. Another system effects control of mechanical devices by establishing a high initial pressure and then bleeding off pressure in a programmed fashion.
Another prior art system is disclosed in U.S. Pat. No. 3,227,228 (1966) assigned to Bannister. This patent teaches the use of a liquid injector to inject liquid into a liquid-filled well bore to create a pressure pulse. The pressure pulse travels down the liquid-filled tubing and is detected as it passes a pressure transducer projecting out into the fluid. The signal from the pressure transducer is used to actuate a downhole tool. As with the Baker xe2x80x9cEDGExe2x80x9d system, the conduit through which the pulse is to be sent has to be completely filled with liquid for the system to work.
There is a need, therefore, for a remote control system and method which will function reliably in actuating a remote tool or other equipment, whatever the nature of the media in the confining elongated bore. Preferably, it should be useful in a wide range of well drilling and completion operations, including MWD, and in pipeline applications which are generally horizontal. The system and method should ensure against accidental triggering of the remote device and be essentially insensitive to extraneous operating conditions and effects. It should also be capable of remote control of selected individual ones of a number of different devices, and providing redundant modes of detection for enhanced reliability and communication capability. While retaining the higher degree of reliability, the system should preferably also require substantially less setup and operating time for field installation and actuation.
MWD installations currently in use require communication with bottom hole assembly (BHA) measuring equipment such as sensors, instruments and microprocessors. The MWD equipment stores information on many parameters including but not limited to bit direction, hole angle, formation evaluation, pressure, temperature, weight on bit, vibration and the like. This is transmitted to the surface using mud pulsing technology. Communicating to the MWD equipment for the purpose of controlling movable elements (i.e., to adjust the stabilizer blades to control direction) is, however, another matter, since not only must commands be given, they must actuate the proper tool and provide sufficient data to make a quantitative adjustment. The current methods use changes of pump rate, and changes of weight on the bit, both of which take time, are limited in data rate, and increase the chances of sticking the drill string.
Remote control of elements in pipelines is a significant objective, since pipeline pigs are driven downstream for inspection or cleaning purposes and can stick or malfunction. Some pigs include internal processor and control equipment while others are designed to disintegrate under particular conditions. The ability to deliver commands to a pig or a stationary device in a remote location in a pipeline is thus highly desirable.
Applicant has discovered and shown that a brief high amplitude pressure impulse will propagate into and through media of different types in a well bore. The pressure impulse transforms during propagation into a time-stretched waveform, at low frequency, that retains sufficient energy at great depth, so that the leading and trailing edges of its transformed profile are readily detectable by modern pressure and motion responsive instruments.
Systems and methods in accordance with the invention utilize a high energy, very short duration, pneumatic impulse transmitted into a tubular or annular system such as exists within a well bore or pipeline. Pressure at a selected level from a gas source is abruptly expelled from a chamber of chosen volume through an orifice into an entry zone, creating an impact burst reaching a very high peak amplitude. Preferably, the pressure level used for supplying pneumatic energy is in the range of 100 to 15,000 psi, the time needed to open into the orifice is of the order of a few milliseconds, and the pressure confining chamber is in the range of 2 to 200 in3 in volume. This energy is dissipated substantially and differently during transmission through long paths in the media, or combination of media, that fills the tubular system. However, the pressure impulse transforms into an extended wavetrain having dominant frequency components, usually below about 200 Hz. Significantly, the pressure impulse traverses the interface between zones of different impedance, such as between a gas level above the top of liquid media in the well bore. Furthermore the impulse propagates without substantial attenuation within the tubular system or annulus, whatever the liquid media or mixture of media in the path. These are referred to herein as xe2x80x9cmobile fluid media.xe2x80x9d
Since it is usually known whether the media is liquid, gas, or successive layers of the two, or contains particulates or other solids, and since well depth is known, the attenuation can be estimated and the energy impulse can be adjusted accordingly. In all instances, wave energy transformation during transmission follows a generic pattern. The pressure impulse is not only diminished in amplitude but is spread out in time, and the brief impulse transitions within the confining structure into what may be called a xe2x80x9ctube wavexe2x80x9d This is a sequence of high amplitude waves at a low frequency approximately determined by the diameter of the tubular confinement structure. These xe2x80x9ctube wavesxe2x80x9d, known and defined in seismic applications, contain ample acoustic wave energy at the deep down-hole location to generate signals of high signal-to-noise ratios.
The pressure variations derived from an input burst are typically of a fraction of a second in total duration. At the remote location one or more transducers respond to physical perturbations of the media to generate separate electrical signals for associated threshold detection, amplifier and decoding circuitry that can recognize signal coding sequences. The signal coding is in the form of a series of time distributed wavetrains above some threshold level, which series represents a binary data sequence. Detection is not frequency or duration based, although the communicated energy varies within frequency and time spaced limits. The components of each series are adequately separated in time to prevent ambiguity arising from possible overlap of the time spread sequences at down-hole targets. The control system circuitry then activates its local energy source to operate the tool selected by the coded sequence in the manner indicated.
The system and method thus imparts an initial high energy burst that assures that wave energy reaches the deep target location in the form of predictable pressure variations. The received signals are so modulated and distinct as to provide a suitable basis for redundant transmissions, ensuring reliability. The system is tolerant of the complex media variations that can exist along the path within the well bore. Differences in wave propagation speed, tube dimension, and energy attenuation do not preclude adequate sensitivity and discrimination from noise. Further, using adequate impulse energy and distributed detection schemes, signals can reach all parts of a deephole installation having multiple lateral bores.
In a pipeline installation, this method of imparting a high energy, impulse is particularly effective because with the uniform media in the pipeline an impulse can traverse a long distance. Thus, an instrumented or cleaning pig can be commanded from a remote source to initiate a chosen control action or pig disintegration.
The concept is particularly suitable for MWD applications, which include not only directional controls, but utilize other commands to modify the operation of down-hole units. The MWD context may require many more encoded patterns, in order to compensate for the dynamic variations that are encountered by the MWD equipment during operation.
The system is also applicable to subsea oil and gas production installations, which typically interconnect a surface platform or vessel via pipelines to a seafloor manifold system communicating with subterranean well bores. By impulsing at the surface with complex coded sequences, systems on the seafloor and down hole tools can be addressed and controlled via the pipelines.
Further in accordance with the invention, the sensor equipment at the remote location may comprise a pressure sensitive device such as a hydrophone, a strain sensor, motion sensitive devices such as a geophone or accelerometer, or a combination used in redundant and mutually supportive fashion. Accommodating the fact that the propagated waveforms, durations and times are modified not only by the transmission distance but by the media, this redundant capability assures further against accidental triggering or actuation of the remote device. Impact forces and pressures generated mechanically or transmitted from other sources through the surrounding environment thus are even less likely to affect the remote tool.